1. Technical Field of the Invention
The present invention relates to cellular telephone networks and, in particular, to the delivery of digital data messages in a dual (analog/digital) mode cellular telephone environment. The invention addresses both the scenario where the cellular telephone is analog, digital, or dual mode, as well as the scenario where the cellular telephone network infrastructure supports analog, digital or dual mode operation.
2. Description of Related Art
Reference is now made to FIG. 1 wherein there is shown a block diagram of a conventional cellular telephone network 10. Many such networks 10 support a short message service (SMS) for use by subscribers in conjunction with the conventional cellular telephone service. The purpose of the short message service is to provide a means for transferring textual messages between short message entities (SMEs) 12 using the communications environment provided by the cellular telephone network 10.
The short message entities 12 participating in the short message service comprise short message terminals (SMT) 14 connected to the cellular network 10 or to the fixed telephone network 16 (comprising a public switched telephone network (PSTN) or other equivalent telephone network). The short message entities 12 further comprise the subscriber mobile stations (MS) 18 operating within the cellular telephone network 10. Short message service messages must originate with or terminate at one of the subscriber mobile stations 18.
A short message service center or message center (MC) 20 is connected to the fixed telephone network 16 and to the cellular telephone network 10. The message center 20 functions as a store and forward center for receiving and delivering short message service messages between the short message entities 12. In those instances where delivery of a short message service message to a short message service entity 12 fails, the message is stored in the message center 20, to be subsequently delivered by the message center to the addressee short message entity at a later time.
The cellular telephone network 10 further includes a plurality of base stations 24 (only one shown) for effectuating radio frequency communications over an air interface 26 with the mobile stations 18. Each base station 24 is connected to a mobile switching center (MSC) 30, with at least one mobile switching center connected to the fixed telephone network 16. The mobile switching center 30 operates to control base station 24 operation, maintain a record (in a home location register 42 as well as its visitor location register 44) of mobile station 18 operating parameters and location within the network 10 and switch, with the fixed telephone network 16, those cellular telephone calls originated by or terminated at the mobile stations 18. The mobile switching center 30 is further connected to the message center 20 used in providing short message services.
Delivery of a short message service message to a short message service entity 12 originates at the message center 20 where a query is sent to the home location register 42 associated with the addressee mobile station 18. Responsive thereto, the home location register 42 provides the message center 20 with information relating to the status of the addressee mobile station (such as active/inactive, currently serving mobile switching center 30, etc.). Provided the mobile station 18 is in the proper state to receive a short message service message, a short message service delivery point-to-point (SMSDPP) invoke communication is generated and transmitted from the message center 20 to the mobile switching center 30. At the mobile switching center 30, the associated visitor location register 44 is queried and a response is received indicating current mobile station state for receiving the message. Provided the mobile station 18 is in the proper state, the mobile switching center 30 pages the addressee mobile station via the base station 24 through which the mobile station made its last system access. If the mobile station 18 answers the page, the message is delivered to the addressee mobile station by means of a transmission made over the air interface 26, generally using the digital control channel (DCC).
Digital data message services (like short message service (SMS) message delivery, and unstructured supplementary service data (USSD) message delivery) are currently offered only to those subscribers having either a digital capable cellular telephone or a dual mode capable cellular telephone. Delivery of the SMS or USSD message invoke communication fails if the addressee mobile station 18 is, at the time of attempted delivery, operating in an analog mode. This is because the analog type of air interface, and in particular the analog control channel (ACC), typically does not support digital data message delivery. There is a need then for a system to facilitate the delivery of digital data messages to dual mode mobile stations operating at the time of message delivery utilizing the analog air interface. It is further recognized that a large number of analog only operable mobile stations exist, and would appreciate having access to digital data message services. There would be an advantage then if the solution for delivery of digital data messages to dual mode mobile stations operating over the analog air interface could also support such message deliveries to analog only capable mobile stations.
Digital data message services further are currently offered only in those service areas supported by digital or dual mode capable mobile switching centers. This is because analog mobile switching centers are not capable of digital message handling operations. There would be an advantage then if delivery of digital data messages could be accomplished through an analog mobile switching center.